Candy Cane Coral looking rinkly

[MiloVW]

Hi,
Im Milo, only 7 months into the hobby and I have made a lot of mistakes along the way. One of my mistakes was not reaching out for help on forums so that's what I'm doing now.
I own a 55 Liter (14.5 GAL) Nano reef tank. I have very little experience with corals and I have lost 5 corals but I dont want to lose any more.
My dad bought me a candycane coral as a gift a little over two weeks ago and today when paying close attention to it I notice these little gaps and rinkles, I don't know if it's splitting heads or if it's tissue is damaged. Hopefully someone can help.
Thanks in advance
The rinkled part is about the top front polyps, there are these dents. Also the far bottom one is a little closed up (this picture was taken from the side of it though, its not that bad) is it not getting enough light?

 

[Bosreef]

Looks like its receding and starting to show its Skeleton...

You say you lost 5 corals I'm sorry.
Post a little more info on your tank.
Parameters salinty? Ph? Alk? Calc?

What are you using for water change water? What are the parameters?
What are you using for top off water?
What are you using for water movement?
What are you using for lights ?
Whats your filteration methods?

 

[MiloVW]

Thank you for you response, I will add info where I can.
Sadly I don't have tests for everything yet (I thought I did before starting, turned out while learning I needed more.)

Salinity: 1.025
Ph: 8.1
Nitrite: 0
Nitrate: 30
Phosphate: 0
Alk: no test, (1 week ago my ''LFS'',1 hour drive away, said it's okay)
Calc: no test, LFS didnt say anything I don't know if they tested it.

Water change water: saltwater from LFS, salinity: 1.025
Top off water: freshly created RODI water using an OsmoPure 50BA
Water movement: one ''Koralia Nano Flow Pump 900L/hour
Filtration: Tunze 9001 Skimmer
Lights: 24 Watts, Lancia ZetLight Series 2 ZP4000-590M (59 centimetres) Controllable ABCD lights by an app which switches to the time of day and appropriate lighting amounts and colors.