Hi,
Myself and my boyfriend have recently bought a 60l tank, we've fishless cycled it which took about 5 weeks, and bought our first lot of fish on Saturday, but I have a few questions about them.
We've got 6 neons, 3 endlers and a betta. Unfortunately one of the endlers went missing, and we found it inside the filter, and a second one died yesterday

. One of the two who were left yesterday was swimming around the surface of the water quite fast, and going into the glass here and there, and the other seemed to just be swimming normally. The single one left now, is swimming around at the surface a lot tonight and he hasn't seem interested in food at all (none of them did really).
The tetras seem to be fine, swimming normally, eating etc.
We haven't seen the Betta eat, and he seems a little subdued, spending a lot of time at the bottom of the tank, or hiding in an ornament. I have however read that they often like to rest, and can take a while to adjust to a new tank. We are feeding them all flakes at the moment, would something else be preferable for the betta/endler?
After the tank had cycled we did a 50% water change, and today we did about a 25% one. Currently the ammonia/nitrites are at 0, nitrates are between 20-40ppm and the PH is around 7.8. Could the PH be too high?
Hope someone has made it to the end of reading this post who can help me

Thanks!