Do you have the datasheet for the LEDs or a complete part number? In order to help you, we have to have all the specs. For example, you stated you have 28 LEDs all wired in series. If the forward voltage of those LEDs is 3 volts, you will need a power supply with a minimum voltage of 84 volts just to turn them all on, but you will only need 1 amp of source current. But, if one “opens” you will lose them all since the current path will be broken. If you wire them all in parallel, you will only need a 3 volt power supply, but it would have to source 28 amps if you want to adjust them up to maximum current (which you don’t). Obviously not ideal. But if one “opens” the rest will stay on. You need a combination series parallel circuit so that if you lose a string, you don’t lose all your light. It’s a balancing game.
Hope this helps.