did you check the guppy profile? https://www.fishlore.com/Profiles-Guppy.htm
we keep our guppies at 78F (25-26C) with a pH of about 7.4 (local pH). It's within their ability to adapt to and they were bred locally. Most fish get used to the local pH and just need it to be kept steady. I'd say your gups are in favourable conditions but you may be dealing with stock that has inbreeding or other poor breeding methods behind it. Trying a new supplier or local breeder is a good idea.
what are the ammonia, nitrites and nitrates levels on your tank? do you have a liquid water testing kit?
thanks for that advice and yes I do have a water test kit I have API freshwater master test kit and my levels are
nitrite 0 ppm
think they are fine but what do you guys think??
I havn't got an airpump is it a good idea to have on or does it not really matter??
also if I should have one what's a good setup in respect of airstone,air curtain that type of thing
well I been out and got an airpump with a diffuser pipe which gives a curtain of air but its very noisy its not the pump cos that quiet but when I connect the air line its resonating badly, why???
do you mean if you disconnect the tube in the tank? if you have the hose hooked to the pump and going into the water, but not hooked to the stone is it still noisy? do you have another airstone to try if it's the airstone that's noisy? does the airstone vibrate any?
non-return valves are a real pain at times. Some work well, orthers are hopeless. The best way around the problem is to put he pump higher than the water, so that it cannot become a siphon if the pump is switched off. You won't need a NR valve at all then.