Can't find error in code

I have a piece of code that seems to not be working properly and I can’t seem to figure out why… Basically, I have a nuke button that “kills” all enemies currently spawned, and this is activated by pressing a UI button. The nuke function itself works fine, however after using the nuke button once in a game, another nuke is used every time the space bar is pressed on the keyboard…

Here is the code for the nuke button:

public void NukePowerup(){
		if (nukeCount > 0 && !gameover) {
			nukeCount--;
			PlayerPrefs.SetInt ("nukeCount", nukeCount);
			enemies.AddRange (GameObject.FindGameObjectsWithTag ("Enemy1"));
			int one = enemies.Count;
			enemies.AddRange (GameObject.FindGameObjectsWithTag ("Enemy2"));
			int two = enemies.Count - one;
			enemies.AddRange (GameObject.FindGameObjectsWithTag ("Enemy3"));
			int three = enemies.Count - two - one;
			enemies.AddRange (GameObject.FindGameObjectsWithTag ("Enemy4"));
			int four = enemies.Count - three - two - one;
			scoreMultiplier += enemies.Count;
			int gains;
			if (nukeLvl == 1) {
				gains = ((one * 100 * scoreMultiplier) + (two * 130 * scoreMultiplier) + (three * 170 * scoreMultiplier) + (four * 300 * scoreMultiplier));
				if (charNumber == 3) {
					gains = (int)(gains * 1.2f);
				}
			} else if (nukeLvl == 2) {
				gains = ((one * 150 * scoreMultiplier) + (two * 195 * scoreMultiplier) + (three * 255 * scoreMultiplier) + (four * 450 * scoreMultiplier));
				if (charNumber == 3) {
					gains = (int)(gains * 1.2f);
				}
			} else if (nukeLvl == 3) {
				gains = ((one * 200 * scoreMultiplier) + (two * 260 * scoreMultiplier) + (three * 340 * scoreMultiplier) + (four * 600 * scoreMultiplier));
				if (charNumber == 3) {
					gains = (int)(gains * 1.2f);
				}
			} else {
				gains = ((one * 100 * scoreMultiplier) + (two * 130 * scoreMultiplier) + (three * 170 * scoreMultiplier) + (four * 300 * scoreMultiplier));
				if (charNumber == 3) {
					gains = (int)(gains * 1.2f);
				}
			}
			score += gains;
			if (scoreMultiplier <= 1) {
				Scorepopup.text = "+ " + gains.ToString ();
			} else {
				Scorepopup.text = scoreMultiplier.ToString () + " Chain 

" + "+ " + gains.ToString();
}
Text scorepop = Instantiate (Scorepopup) as Text;
scorepop.transform.SetParent (GameObject.Find (“Canvas”).transform);
scorepop.transform.localPosition = transform.position;
foreach (GameObject enemy in enemies) {
if (enemy != null) {
enemy.GetComponent ().useGravity = true;
enemy.tag = “dead”;
}
}
scoreMultiplier = 0;
usedNuke = true;
checkChallenges ();
powerupsUsed++;
PlayerPrefs.SetInt (“powerupsUsed”, powerupsUsed);
}
}

The only code I have relating to the pressing of the space button in the script is as follows:

void FixedUpdate(){
isGrounded = Physics.Raycast (transform.position, Vector3.down, 0.565f, groundLayer);
if (Input.GetAxis ("Jump") != 0f && isGrounded) {
				if (!killBox.GetComponent<AudioSource> ().isPlaying) {
					killBox.GetComponent<AudioSource> ().Play ();
				}
				GetComponent<Rigidbody> ().AddForce (new Vector3 (0, Input.GetAxis ("Jump") * jumpPower, 0), ForceMode.Impulse);
			}
}

Any help would be greatly appreciated, as I have absolutely no clue what is causing this…

UI.Button → Navigation → Set to None

https://docs.unity3d.com/Manual/script-SelectableNavigation.html