While i wouldn't say you are overcrowded, i would question your stocking.
Those tetras are better kept in larger groups than 4. It would be better to pick one type and have 8, rather than 4 of each.
Same can be said for the loaches and corys, 3 or 4 loaches and 6 corys. Pick 1 and up the numbers.
I dont have experience of keeping female bettas, but have read that they need space to keep out of each others way, and 60 litres doesn't give them that.
If you really want to keep all those fish together then getting a bigger tank and upping the numbers would be a good idea. They will be much healthier and happier in bigger groups.