Any advice

I think Mrs FP's fry are somewhat larger than recently hatch fry?
Here are a couple of methods which have worked for me down the years, one is to use a fairly deep net which you sink into the tank with some either sinking pellets or, when I used to use them, frozen Bloodworms. Eventually the fish will overcome their distrust of the net and venture into it after the tasty morsels, this is where the sinking pellets have the advantage as they will stay in the net more than would Bloodworms or the like.
This is a bit of a waiting game and you will need another net to put in sharply (once the fish you want to catch are in the first net and feeding) to block off the escape route.
This isn't foolproof but works pretty well.
My other ploy to catch 'difficult' fish is to make a trap from a plastic drink bottle. You cut the 'shoulder' of the bottle at the point where it starts to taper in to the top - and then you're left with a sort of funnel. This is then reversed and jammed into the bottle the wrong way around making a crude 'funnel trap.
You need to make a few holes in it to keep it submerged and I usually put in some coarse gravel to keep it in place on the bottom of the tank. You then - once again - put in some tit-bits and await results. The fish find it easy to follow the funnel into the trap but they don't manage to escape quite as easily as now they only have the hole the size of the bottle top to escape from.

I hope this is making sense?

A small word of warning here though - if any of your Corys venture into the trap they should be released pretty promptly, as there is no water surface for them to rise up to for air they quickly become stressed - I have even had them die in a trap such as this.

Your Kribs will be OK though - and anything else which ventures in, just watch out for the Cats!

Good luck in your quest, but deep down my suspicion is that you might need to fall back on the netting them method - with the subsequent upheaval of your tank.

John