Hello. Based on the attached photos and the information provided, it is most likely that the plant’s deterioration is the result of a combination of biotic and abiotic factors, such as the stress suffered during transport, handling and during the changes in the environmental conditions, possibly because of the constant high humidity of the substrate, maybe due to the presence of phytopathogenic agents, etc. It is recommended that watering be carried out moderately, so that the substrate is allowed to slightly dry beforehand. It is recommended to regularly remove the severely affected leaves. Subsequently, you may consider 1-2 treatments, 7-10 days apart, with a systemic fungicide with a broader spectrum of control, such as , in a dose of 10 ml/10 L water, applied by foliar spraying. Spray the solution as finely as possible, so as to achieve an even distribution on the plant, both on the underside and topside of the leaves and on the stem (). It is advisable to prepare a volume of solution corresponding to a single treatment (respecting the mentioned dosage), as the already prepared mixture does not have a shelf life longer than 24 hours.
Additionally, to improve the quality of the substrate and ensure the required nutrients, it is recommended to use a fertilizer such as , according to the instructions in the product description. You can also periodically apply your own foliar fertilizer as recommended in the product description ().
Subsequently, starting in spring (throughout the growing season), it is recommended to regularly apply , as recommended on the label.
Further, it is recommended to ensure the optimal conditions for this species. More information on this subject can be found in our articles: Citrus, plant care and growing guide and Citrus, pest and disease control, respectively Indoor plant placement according to environmental factors. The future evolution of the lemon tree cannot be precisely predicted.