I have a 75 gallon tank with an external canister filter and a LED light bar with multiple lighting features on a timer
Okay... let's start with the tank size.
In my opinion, a 75 gallon tank is a good size for a first setup. Chemistry fluctuations in rookie reef tanks are not uncommon. But the larger the tank, the more subtle these changes are. So while you may have fluctuations in your water chemistry, you will have more time to identify and correct it before it becomes a problem.
My experience with canister filters are that they work well. However you must be committed to faithful cleaning as they can quickly become Nitrate (NO3) factories, which can lead to nuisance issues such as algae growth taking over your display. Also, faithful water changes will be critical in keeping your nutrient levels down as you haven't mentioned if you are using a protein skimmer. I would recommend a FAITHFUL weekly water change of 20%. In a 75 gallon tank, this is 15 gallon water change every week.
You haven't mentioned a brand where your lighting system is concerned, so I assume it is a generic system which tries to emulate features on high-end lighting systems. If this is true, it may look like a capable light, but it probably isn't capable of supporting anything more than fish in the tank, or what we commonly refer to as a FOWLR tank. This stands for
Fish
Only
With
Live
Rock. I would NOT try placing coral frags or Anemones in a tank with generic lighting.
If you provide more info on the lighting, the information we can provide will be more accurate.