Help L397 fry dieing

[cca001]

Hi all I need some help please.
My L397 babies were fine for about 10-14 days then some started getting very fat stomachs like bloat and are dead within 24hrs
I haven't fed them yet after reading up a little on them.
I just let them forage around and eat algae or munch on the bit of driftwood in there.

I have checked the water parameters and the nitrate , nitrite , ammonia , copper , phosphate are well low or non existent.
Would post photos but computer is dead atm so posting from phone.
However I have posted photos on the plecoplanet Facebook page.

Any advice would be greatly appreciated.

 

[Nat's Fish]

I feed them slightly blanched zucchini as soon as their egg sacs dissolve & they all smash it. They are probably starving to death. Do you have gravel or a bare bottom tank?

 

[cca001]

They have a gravel bottom tank which has some crypts and vallis in there with them aswell as driftwood.