I am assuming that you cycled this tank before getting the fish. If this is not the case then your issue is a lot more complex than thought.
How you shot the picture makes it difficult to tell the exact levels especially for ammonia. The filled part of the tubed needs to be next to the color bars to which it appears closest.
From what I can see reliably from your pic what I concluded from your pic was as follows.
pH- I would have suggested you do the high range test and you did but there is no pic. So, I will trust your 8.0 reading was accurate.
Ammonia- this was hard to read for sure do do the vial being out of position and not near the top bars where it should have been placed. That said whether or not a water change is the correct thing to do requires that we know how much of that reading is in the form of NH3 (ammonia) most of it will be NH$ (ammonium) which is nowhere near as dangerous.
r
Determining these two numbers requires knowing the pH and the temperature of the water- the higher these are, the more of the ammonia will be in the toxic form. I did not see any ibfo on temp. from you so I ran the calcs at a few different temp. levels and using the 8.) you reported on the high range test
At 76 F, the NH3 = 0.0131 ppm- This not dangerous and you should do nothing, do not change water. The bacteria will fix this fast.
At 78 F, the NH3 = 0.0143 ppm- This not dangerous and you should do nothing, do not change water. The bacteria will fix this fast.
At 80 F, the NH3 = 0.0155 ppm- This not dangerous and you should do nothing, do not change water. The bacteria will fix this fast.
If your pH is actually higher, then the numbers above would be higher.
Ammonia tests can give false readings which cause such a low level to read as ammonia but which is actually something else. Foir exampple, iron in the water can interfere with test accuracy.. So it is possible you actually have no ammonia at all.
Nitrite- is at 0 and not a worry. And this reinforces my belief that the ammonia reading could be a false one. This especially assumes that you had cycled the tank. If you did not then this should be be rising either now or soon.
Nitrate- is also 0. This would normally bother me in terms of is the tank cycled, but the water change you did would be enough to lower a small level of nitrate to 0.
Because of the other fish in the tank, ammonia should be much higher than .25 ppm if the tank had not been cycled. So, despite what others have suggested I would tell you to ignore it and keep testing. If the ammonia level increases or if nitrite shows up, then you now there is an issue. If so read here,
https://www.fishforums.net/threads/rescuing-a-fish-in-cycle-gone-wild-part-il.433778/
I think you already know about this article