Not so much a question as a number of answers to deficiency symptoms.
– Yellowing of older leaves on plants, followed closely by the entire plant coupled with slow growth indicates Nitrogen (N) deficiency.
– Older leaves turning dark green followed by purple discolouration of leaf edges indicate Phosphorous (P) deficiency.
– Leaf tips turning brown and drying with leaf edges looking burnt and brown indicate Potassium (K) deficiency.
A: Consider using a fertiliser but if you’re unsure when and what to apply, as a guide use one with NPK in early spring, a light Nitrogenous N during summer then lastly N and K in the autumn.