I have 4 seemango seeslings and a single strawberry cheesecake.
The 2 in the first photo have a week head start with the seemango being trapped by seed shell.
The 3 other seangos I only placed in soil yesterday morning and they've already started to stand up and change their shoot colour to a crimson red.
They've been planted into the fiber pots with a equal mix of black magic seed rasing soil mix: perlite: spag moss.
A small amount of Acid food and Blood and bone ferliser add into the soil mix.
Given each seedling only 100mls of ph'd water
I would just flush with clean water. plant is so young i would not mess with top dressing etc right now. Ph your water to 6.00-6.5 and asses from there